It's All In The Expression

Changes in the expression level of certain genes may underlie some of the fundamental differences between humans and chimpanzees, suggests a study in 09 March 2006 issue of Nature (Vol. 440, No. 7081, pp 242-245). Previous studies have concentrated on comparing the genomic sequences themselves, but by looking at the levels of gene expression we may gain new insights into the selective pressures driving genome evolution.

Gilad and colleagues compared gene expression in humans, chimpanzees, orangutans and rhesus macaques. Using a multi-species gene array, they were able to identify a series of genes that have been expressed at a stable level throughout the 70-million-year evolution of these species. The authors found that several of these genes are associated with human disease, suggesting that this property (constant levels of expression over evolution) may be used to identify other disease gene candidates.

A small number of human genes show a rapid divergence in the level of expression when compared with the other primates. Most of these genes are upregulated, and they encode transcription factors, which are often linked with divergence at the organismal level. The authors propose that differences in the expression of these genes could account for the large number of phenotypic changes in the human lineage.